The present invention relates to load boards for testing integrated circuits, and particularly to mounting a load board onto a test head.
A test head and a load board are used to test the functionality of newly manufactured integrated circuits. The integrated circuits to be tested are connected to a load board prior to testing. The test head provides power and controls the flow of electricity to the integrated circuits attached to the load board 325 (FIG. 9) during testing. As seen in FIG. 3, a test head 310 may be circular in shape and have an aperture through the middle. Channel cards 315 are arranged around the circumference of the interior aperture 312 and contain pogo pins 320 on the upper surface of the channel cards 315. As seen in FIG. 12, pogo pins 320 are spring loaded pins, for example the pin portion 322 is able to recede into the spring containing portion 324, that provide electrical contact between the test head channel cards 315 and the load board 325 via slots 326 on the underside of the load board 325.
Load boards are electromechanical printed circuit boards used for testing the functionality of integrated circuits. A load board is latched onto a test head, and therefore, must be properly aligned with the test head so that the pogo pins 320 correctly contact the load board. Proper alignment ensures electrical contact between the test head channel cards 315 and the load board 325 so that the test head fully conducts testing of the integrated circuits. A schematic depiction of a load board 325 in electrical contact with the pogo pins 320 of a test card 315 that is connected to a test head 310 is provided in FIG. 13. A slot 326 on the underside of the load board 325 is depicted as the contact point between the pogo pins 320 and the load board 325.
Load boards are normally manually positioned onto test heads, leading to several concerns. Manually positioning a load board onto a test head makes it difficult to properly align the load board with the test head, which may result in improper contact of the pogo pins 320 with the load board 325. As a result, load boards are often shifted or adjusted after initial manual positioning in order to align the load board with the test head. However, the pogo pins 320 that the load board is already in contact with are spring loaded, and therefore, easily bent or broken. A damaged pogo pin 320 requires replacement of the channel card 315 that the damaged pogo pin 320 is part of, each channel card normally being very expensive. Replacing a channel card 315 also leads to test head down time, which delays production and causes additional expense.
There is a need to prevent bent and broken pogo pins on a test head channel card related to testing integrated circuits. There is also a need to ensure that load boards are properly aligned with test heads. These needs and others are addressed by the present invention, which provides alignment of the load board with the test head, and an automated system for positioning the load board onto the test head. According to the present invention, a load board feeder is installed into the center aperture of a test head. The load board feeder has a location device that engages the load board when the load board is properly aligned with the test head. The load board feeder also comprises a mechanism for lowering the load board into its seating place on the test head, without a damaging impact to the pogo pins on the test head channel cards. This mechanism prevents undue damage to the delicate pogo pins on the test head channel cards that may occur during manual positioning and alignment of the load board.
Accordingly, one aspect of the invention relates to a load board feeder for positioning a load board onto a test head that has an aperture through its center. The load board feeder comprises a base and a body connected to the base. An attachment device is connected to the body and is used to attach the load board feeder to the test head. A lift mechanism is connected to the base and vertically moves a block that is attached to the lift mechanism. The block contains the load board location device and serves as a resting place for the load board prior to positioning the load board onto the test head.
In certain embodiments, the load board feeder is cylindrically shaped, and contains a load board location device on a circular block. The load board location device comprises a circular plate attached to the block and a disk that engages the block and the plate. The circular block has a circular cavity that is not concentric with the center of the block. Likewise, the circular plate has a non-concentric, circular hole that aligns with the circular cavity in the block. The outer diameter of the circular disk is just small enough to allow the circular disk to fit within the circular hole and cavity. The top of the circular disk protrudes above the top of the plate, thereby providing an engagement element for a load board.
Accordingly, another aspect of the invention relates to a method of seating a load board onto a test head having an aperture through its center. A load board feeder, comprising a lift mechanism and a location device for aligning a load board with a test head, is attached within the center aperture of a test head. The load board feeder is brought to its raised position and a load board is placed onto the load board feeder. The load board is adjusted so that it engages the load board location device. The load board is aligned with the test head when the load board engages the load board location device. The lift mechanism is activated to lower the load board into its seating position on the test head and the load board is latched to the test head.
Other advantages of the present invention will become readily apparent from the following detailed description, simply by way of illustration of the best mode contemplated of carrying out the invention. The invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are illustrative in nature, not restrictive.